1. Field of the Invention
The present invention relates generally to a method of and an apparatus for marking through-bores in walls, ceilings and other structural components of rooms and buildings. More particularly, the invention relates to a method and an apparatus of the kind referred operating by electromagnetic or ultrasonic radiation.
While such methods and apparatus are generally useful in all situations where entrance and exit openings of a bore or channel disposed in opposite surfaces of a structure need be defined precisely before such bore or channel, hereinafter sometimes referred to as "perforation", is drilled or sunk, they are of particular advantage when the surfaces in which entrance and exit openings of a perforation are disposed are not readily accessible at the same time to allow a precise determination of their respective position, or where the configuration of the two surfaces is so dissimilar as to defy an easy definition of these position by mechanical measurements.
2. The State of the Art
Marking the positions of entrance and exit openings of perforations in walls and the like by indirectly measuring longitudinal dimensions and angular degrees, even around a plurality of corners, curvatures and edges, has for a long time been standard practice in the building trades. Taking such measurements does, however, pose special difficulties and is a very disadvantageous and inefficient way of defining the course and direction of a perforation and its entrance and exit openings, particularly in building and rooms in which technical equipment is housed, such as, for instance, production machinery, workshops, laboratories, switching stations as well as installed electrical and plumbing facilities. Further difficulties present themselves in connection with front walls or facades of buildings.
It has also been know to sink test bores at non-hazardous and/or unobtrusive positions to establish reference points for placing marks for an actual perforation. This, too, however, is rather a complicated and involved way of placing indicia for through-bores and is unsuited for marking facades or in living, business or social function rooms.